Posted: Mon 20th May 2024

Public urged to help to tackle spread of invasive Chinese mitten crab in Wales for people living in or visiting the Wrexham area

Natural Resources Wales (NRW) is calling on members of the public to help stop the spread of the only species of crab that can be found in UK freshwaters.

The Chinese mitten crab, an invasive non-native species (INNS) which poses a threat to biodiversity.

According to NRW the Chinese mitten crab is already established in the Dee estuary and has now been confirmed in the Conwy estuary.

Rare sightings have also been recorded in the Severn estuary and NRW is encouraging people to record any sightings on the iRecord app or online so they can better understand their impact and spread.

The species are known to eat rare salmon eggs, large quantities of mussels and so much river vegetation that they can cause major damage to river courses.

They can carry diseases such as lung fluke and crayfish plague, and will outcompete and predate on the protected, white-clawed crayfish, as well as damage flood assets by burrowing.

Adult Chinese mitten crab spend four to five years in freshwater and move down to estuaries to breed and spawn before they die. Their plankton develop in the estuary, and then juveniles move back upstream.

Jennie Jones, Specialist Advisor for Invasive Non-Native Species at NRW said: “Protecting biodiversity is so vital in tackling the climate and nature emergencies. It is important to take action to tackle INNS that pose a threat to native wildlife.

“Most non-native species are harmless, but around 10-15% can become invasive and cause harm.

“These types of invasive non-native species, like the Chinese mitten crab, outcompete some of our native biodiversity and cause damage to the environment.

“There are ways we can all help to prevent the spread of these species, including carrying out biosecurity, recording your sightings and joining a local action group.

“We really encourage people to get to know what these invasive species are, and record their sightings through the iRecord app or through its online space that collects information about where these non-native invasive species are being seen.”

Invasive non-native species are one of the top threats to global biodiversity; 86% of extinctions that have happened on islands were contributed to by invasive non-native species.

It costs Great Britain’s economy over £2 billion a year to deal with the issue, and INNS can even harm human health.

Once an INNS has been introduced it can be difficult to manage, particularly in the marine environment.

The problems it causes will escalate as it spreads further so, preventing the arrival of new non-native plants and animals is essential.

Once they are here, detecting them early and responding rapidly to prevent their establishment is vital, and minimising their negative impacts by slowing their spread if they become established.

To help stop the spread of the Chinese mitten crab and other INNS, there are three simple things everyone can do to help:

  • Ensure you do not accidentally move this species to a new area by checking, cleaning and drying any equipment, clothing or shoes before travelling to a new site. Now is a critical time in the lifecycle of mitten crabs, there will be larva in the water column which cannot be seen but can cling to any equipment you might be using. It is especially important to check clean dry all your equipment at this time
  • Learn how to identify mitten crab and keep an eye out for this species
  • Record any mitten crab sightings via iRecord

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